# what is r times r?

is it 2r or something else?? I need help with math

### 12 Answers

- PuzzlingLv 76 days ago
This can be a confusing concept when you switch from numbers to variables. So let's go back to looking at concrete numbers and see if you can figure it out.

Let r = 5

2r = 10

So it makes sense that r *plus* r = 2r.

r + r = 2r

5 + 5 = 10

But when you are multiplying a number by itself, then you are *squaring* not adding.

r * r = r²

5 * 5 = 5² = 25

For example, if the size of a closet is 5 ft. x 5 ft. then its area is 25 sq. ft. You wouldn't add and say it is 10 ft. That's not even an area, it's just another length.

Summary:

Multiplying a number by itself is the same as *squaring* so the result would be r².

Answer:

r * r = r²

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- PinkgreenLv 77 days ago
Suppose r*r=2r is true for all real number, then

r*r-2r=0=>r(r-2)=0=>r=0 or r=2.

That means 2*2=2(2); 0*0=2(0) are true.

If r=3, then LHS=3*3=9, but RHS=2(3)=6. LHS=/=RHS

=>

r*r=2r can't be true for any real number except r=0 or r=2. It

is a contradiction to the assumption

=>

r*r=2r is not true, in general.

In fact r*r=r^2.

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